Future hand-held and ground communications systems, as well as communications satellites, will require very low weight, and low power consumption in addition to higher data rates and increased functionality. Radiofrequency and microwave circuit boards used in such communications systems integrate discrete passive components, such as high-Q inductors, capacitors, varactors, and ceramic filters, for matching networks, LC tank circuits in voltage controlled oscillators, attenuators, power dividers, filtering, switching, decoupling, and reference resonators. Trends in the design of circuit boards for communications systems include reducing both board size and component count. Passive components consume a substantial fraction of the total board space, which presents challenges in furthering these trends.
To reduce the space taken up by the passive components, discrete passive components are being replaced with on-chip passive components. Size reduction of passive components may depend at least in part on the further development of on-chip interconnects, such as slow wave coplanar waveguide (CPW) structures, for microwave and millimeter microwave integrated circuits (MICs), microwave and millimeter monolithic microwave integrated circuits (MMICs), and radiofrequency integrated circuits (RFICs) used in communications systems. In particular, interconnects that promote slow-wave propagation can be employed to reduce the sizes and cost of distributed elements to implement delay lines, variable phase shifters, voltage-tunable filters, etc.
Advanced methods of coplanar waveguide structures are needed for radiofrequency and microwave integrated circuits to serve as interconnects that promote slow-wave propagation.